Monday, May 27, 2013

Climate Change and Human Innovation

Changes in climate during the Stone Age forced our ancestors to develop new technologies, say scientists.

The research, published today in Nature Communications' looked at sediment cores drilled from the seafloor off the coast of South Africa. The tubes of rock gave the scientists an insight into the area's climate over the past 100,000 years.

They found periods of abrupt cooling occurred over very short time scales, with temperatures sometimes dropping as much as 15oC over a few decades. And, in contrast to the northern hemisphere and monsoon areas which got much drier, South Africa became much wetter.

'During these abrupt events, changes in ocean circulation meant there was less energy and warmth transported to the northern hemisphere and this allowed more heat to stay in the Southern hemisphere and pushed the warmth and rainfall further south, and that is what we then see in southeast Africa,' says Dr Martin Ziegler of Cardiff University who led the study. 'Where large parts of the globe got drier and ecosystems became less favourable, southeast Africa got warmer and wetter, providing conditions that were probably more hospitable for early humans.'

Once they had found this pattern of South Africa getting wetter during these cold events, the team went on to compare the timing against the archaeological record.

'When we compared our climate record to the archaeological record it was clear that periods of innovation in early humans always occurred during the warmer and wetter periods,' says Ziegler. 'Around 80-60,000 years ago we find certain industries in the archaeological record, like more sophisticated tools, the first evidence of symbols and the use of jewellery.'

The now dry Botswanan lake basin was once a sea. It filled with water from the Angolan Highlands. Some of Africa's earliest human populations lived on the edges of this great lake, evidenced by thousands of stone tools found there. The tools include mace heads dating to between 80,000 and 100,000 years.